Iontophoretic delivery of peptides

ABSTRACT

The invention concerns a new system and method for iontophoretically delivering a polypeptide transdermally into animal tissue.

BACKGROUND OF THE INVENTION

This invention relates to a manner of delivering substances into amammalian body, and more particulary concerns delivery of polypeptideinto a mammalian body.

Ionic substances have previously been delivered into body tissue byiontophoretic means. This method for delivering substances such aschemicals or drugs normally utilizes direct electrical current incontact with the skin, and drives these substances through intact skinto the interior of the animal body, including the blood stream.Iontophoresis has been shown to be useful in various medicalapplications and substances such a lidocaine, hydrocortisone and manyother drugs have been so administered.

Various iontophoretic devices and systems have been previously describedand comprise a source for generating current, a pair of electrodes andthe ionic substance to be introduced into the body. The activeelectrode, the donor electrode that drives the desired substance throughthe skin, is of the same charge as the substance.

It is preferable that the active electrode also physically embrace asource for the drugs, and this can be accomplished by retaining the drugin a compatible matrix, such as a polymeric matrix, e.g. a gel or asolution contained by a semipermable membrane, or even a moist cloth orgauze and water system which will permit flow of electrically chargedsubstance to and through the skin. Transdermal patches which contain thedrug, a matrix and water are the preferred mode for transdermallyadministering the active agent to the human or non-human animal patient.

European Patent Application 0278 473 discloses a chemical compositionand system for iontophoretic transport which comprises a protein, acosolvent with negative Setschenow constant and water. The protein whichmay be used includes, but is not limited to, polypeptides having morethan about 20 peptide units. The various proteins mentioned include butare not limited to calcitonin and insulin.

Iontophoretic transdermal delivery of insulin, which is a 51 peptideprotein is disclosed by Chien, et al, J. Pharmaceutical Sciences 78, 5,376-383 May 1989.

It is an object of the present invention to provide a means foriontophoretically delivering transdermally calcitonin, especially salmoncalcitonin, into animal tissue.

It is a further object to provide a method for delivering calcitonin byiontophoretic transdermal means to a human or a non-human patientwithout the use of a cosolvent in the drug reservoir.

A further object is the provision of a transdermal device for deliveringcalcitonin by iontophoresis into animal tissue.

SUMMARY OF THE INVENTION

The invention is a new system and method for iontophoreticallydelivering a polypeptide, such as calcitonin, transdermally into animaltissue.

DESCRIPTION OF THE INVENTION

It has now been surprisingly found that a calcitonin, such as salmoncalcitonin, which is a 32 amino acid polypeptide having a positivecharge, may be iontophoretically introduced transdermally into mammaliantissue by means of continuous application of a voltage difference lessthan about ten volts with a simple aqueous electrode system. No need forcosolvent is required. Instead, a quantity of a calcitonin in a matrixconsisting essentially of water may be driven through the epidermallayer into the blood stream. This avoids the undesirable complication ofalso transporting a cosolvent into the transdermal layer or into theblood stream of the human or non-human animal being administered thecalcitonin.

The levels of calcitonin in the animal blood stream achieved by thismethod are therapeutic, this being accomplished in short periods of timeand without injury or irritation to the epidermal layers.

Generally the matrix containing the calcitonin is in the form of anadhesive patch filled with a gel or polymeric substance capable ofretaining the water and the calcitonin. A pH of 4-9 is acceptable,preferably a pH of 4.5-6, most preferably 4.5-5.5. The gel may consistof aqueous hydroxypropyl methylcellulose or other neutral gel formingpolymers in water.

The electrical components of the electrodes usable are also known in theart and preferably are silver/silver chloride electrodes.

A convenient configuration for the reservoir containing the calcitoninwould a two membrance system whereby the calcitonin, such as salmoncalcitonin, in the gel and water matrix would be retained between thetwo membranes. A two chamber compartment on an adhesive patch, is apreferred embodiment of the iontophoretic system of this invention.

It should also be understood that it is preferred that no other ions oflike charge to the drug be present in the transdermal patch.Preservative to prevent microbiological contamination is also useful. Toavoid driving this preservative into the tissue, it is also understoodthat it should be neutral or negatively charged.

A current density from about 10 microamps (μA) per cm² about 300 μA/cm²may be used, higher currents being possible but increasing the chancesof damage to the tissued involved. The preferrered current density isabout 100-250 μA/cm².

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the mean plasma levels of salmon calcitonin with respect totime in the test animals.

EXAMPLE 1

An iontophoretic device consisting of two patches, one containing adonor gel and a silver wire mesh electrode and the other a returnelectrode, and a constant current source is used. A tared donorcompartment is filled with about 4 ml of 4% hydroxypropylmethylcellulose (Shin-Etsu, Tokyo, Japan) gel containing 12.5 mg ofsalmon calcitonin/g of gel. The weight of the filled patch is measuredto calculate the amount of calcitonin added. The donor compartment isseparated from the silver electrode by an anion selective membrane(Raipore #5030H) and the top chamber contains Signa Gel (Parker Labs,West Orange, N.J.). See Sanderson et al, J. Pharm. Sci. 76,215 (1987)and Parsi U.S. Pat. No. 4,731,049 respecting anion selective membranes.The donor gel is contained inside the patch by adhering a Spectra/Por 2dialysis membrane (molecular weight cut off 12,000 to 14,000 Daltons;Spectrum, Los Angeles, Calif.) to the bottom of the patch. The returnpatch consists of a silver wire mesh electrode plated with chloride anda chamber filled with Signa Gel. The surface area of each patch exposedto the skin is 10 square cm.

EXAMPLE 2

The patches of Example 1 are applied to each of three male miniatureswine both by iontophoresis and passively in a crossover fashion. In thefirst part of the study, two animals receive current while the other isa passive control. For the second phase of the study, animals receivethe opposite treatment; see Table I below. The total current applied is2mA or the equivalent of 200 μA/cm2. The patches are applied for 12hours. After that time the current is stopped and all devices areremoved. The gel remaining on the skin is recovered for analysis ofresidual salmon calcitonin not delivered. The amount remaining in thepatch is determined by removing the excess gel from the patch, soakingthe patch and dissolving the excess gel in pH 5 sodium acetate buffer.

Zero time blood samples are drawn the afternoon of the day before thedevices are applied. Two ml of plasma from each animal is reserved forthe zero sample and the rest pooled for use in the analysis.

Blood samples are drawn at 1,2,3,4,6,8,12,24,28,32,48 and 72 hours. Foreach sample the animal is turned on its back. At least 2 ml of blood isdrawn from the vena cava into plastic syringes using an 18 gauge, 1.5inch needle. The blood sample is transferred into chilled plastic tubescontaining lithium heparin. The tubes are centriguged at 4° C. at 3,000rpm for 10 minutes to isolate the plasma. The plasma is drawn off usinga pipette and transferred to a plastic tube labeled with the number ofthe animal and the sample time. The plasma is stored frozen at -70° C.until all samples are collected. The concentration of calcitonin in eachsample is determined by radioimmunoassay.

Results

The concentration of salmon calcitonin in the plasma for the twotreatments is presented in Tables II and III. The mean plasma levels ofthe three animals at each sample time are plotted with respect to timein FIG. 1. Animal #149-5 aside, there was on average from 20 to 1000times greater calcitonin concentrations with iontophoresis than with nocurrent.

                  TABLE I                                                         ______________________________________                                        EXPERIMENTAL DESIGN                                                           Animal #      Part I       Part II                                            ______________________________________                                        149-1         Iontophoresis                                                                              Passive                                            149-4         Iontophoresis                                                                              Passive                                            149-5         Passive      Iontophoresis                                      ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        SALMON CALCITONIN PLASMA LEVELS                                               FOLLOWING IONTOPHORESIS (mIU/ml)                                              Pig Number                                                                    Time   149-1     149-4   149-5   Mean  SEM                                    ______________________________________                                        0      0.000     0.000   0.000   0.000 0.000                                  1      2.210     1.466   0.372   1.349 0.534                                  2      3.139     4.057   0.099   2.432 1.196                                  3      3.070     4.840   0.222   2.711 1.345                                  4      6.955     4.582   0.022   3.853 2.034                                  6      7.825     5.890   0.000   4.572 2.353                                  8      8.627     8.542   0.000   5.723 2.862                                  12     13.160    13.940  11.070  12.723                                                                              0.857                                  24     1.527     1.368   0.733   1.209 0.243                                  28     0.295     0.302   0.092   0.230 0.069                                  32     0.258     0.404   0.168   0.277 0.069                                  48     0.289     0.149   0.107   0.182 0.055                                  72     0.149     0.169   0.060   0.126 0.034                                  ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        SALMON CALCITONIN LEVELS FOLLOWING                                            PASSIVE ADMINISTRATION (mIU/ml)                                               Pig Number                                                                    Time   149-1     149-4  149-5   Mean  SEM                                     ______________________________________                                        0      0         0      0       0     0                                       1      0.020     0.086  0.031   0.045 0.020                                   2      0         0.115  0.182   0.099 0.053                                   3      0.027     0.055  0.261   0.114 0.073                                   4      0         0      0.295   0.098 0.098                                   6      0.064     0.032  0.431   0.175 0.128                                   8      0.061     0.077  0.579   0.239 0.170                                   12     0         0.035  0.510   0.181 0.164                                   24     0.111     0.695  0.075   0.293 0.200                                   28     0         0.089  0.084   0.090 0.004                                   32     0         0.068  0.103   0.057 0.030                                   48     0.032     0.058  0.065   0.051 0.010                                   72     0         0.053  0       0.017 0.017                                   ______________________________________                                    

The amount of calcitonin placed in each patch, the residual calcitoninrecovered from the patch and the estimate of the amount of calcitonintransported, calculated from the difference between the amount appliedand the amount recovered, are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        SALMON CALCITONIN DELIVERED                                                   Iontophoresis                                                                              149-1       149-4  149-5                                         ______________________________________                                        Mg Applied   38.4        43.7   39.1                                          Mg Recovered 12.4        30.8   35.3                                          Mg Delivered 26.0        12.9    3.8                                          ______________________________________                                    

We claim:
 1. A device for transdermal transport of a chemical intoanimal tissue by electrolytic means comprising a calcitonin and water ina reservoir usable for iontophoretic administration.
 2. A transdermalpatch for delivering a calcitonin into the blood stream of a patienthaving in an electrode thereof a solution consisting essentially of acalcitonin and water.
 3. A transdermal patch according to claim 2wherein said calcitonin is salmon calcitonin.
 4. A transdermal patchaccording to claim 3 wherein the solution additionally contains apreservative.
 5. A method for transdermally transporting a calcitonininto animal tissue which comprises use of a device according to claims 1or
 2. 6. A method according to claim 5 wherein the solution additionallycontains a neutral or anionic preservative.
 7. A method for transportingsalmon calcitonin into the blood stream of a patient which comprisesusing an iontophoretic patch containing in a donor electrode a solutionof salmon calcitonin and water.
 8. A method according to claim 7 whereinthe donor electrode solution consists essentially of salmon calcitoninand water.